Preparation and characterization of polychloroprene/modified clay nanocomposites
Mohomane, Samson Masulubanye
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Nanocomposites are a new class of mineral-filled plastics that contain relatively small amounts (<10%) of nanometer-sized clay particles. Production of rubber-based nanocomposites involves melt mixing the base polymer and layered silicate powders that have been modified with quaternary ammonium salts. In this study, new nanocomposite materials were produced from polychloroprene rubber (PCP) as the matrix and organically modified montmorillonite clays as fillers by using a two-roll mill. PCP was mixed with the clays in contents of 2.5, 5, and 10 phr. Five types of clays (Cloisite 15A, 20A, 25A, 10A and 93A) were investigated during this study and their influence on the thermal and mechanical properties of the rubber was compared. The degree of exfoliation or intercalation of the organoclays in the PCP nanocomposites was investigated using x-ray diffraction spectroscopy (XRD) and transmission electron microscopy (TEM). The results for Cloisite 93A and 15A depicted an exfoliated structure and a welldispersed morphology in the polymer matrix at all filler contents, while complete exfoliation was not observed for the other clays, especially at higher clay contents. The tensile modulus was found to increase with an increase in clay content for all the nanocomposites, while tensile strength and elongation at break decreased. The initial stage of thermal degradation was accelerated with the incorporation of organoclays. The TGA results show that Cloisite 15A and 93A have a significant influence on the PCP degradation mechanism, even at low clay contents. The properties of the PCP/clay nanocomposites were also determined by dynamic mechanical analysis (DMA) and stress relaxation. Cloisite 15A and 93A containing nanocomposites were generally found to have better properties than the other samples. This could be due to these clays having stronger interactions with the PCP rubber.